Trisomy 18p caused by a supernumerary marker with a chromosome 13/21 centromere: a possible recurrent chromosome aberration.

We present a clinical and molecular cytogenetic characterization of two new patients with a complex supernumerary marker consisting of the entire short arm of chromosome 18 with a chromosome 13/21 centromere. One patient is a girl with a nonsyndromic intellectual disability and the second is a prenatally diagnosed fetus. To our knowledge, these are the fourth and fifth such cases to be described in the literature, suggesting the existence of a possible recurring constitutional structural chromosome abnormality.

Application of FISH 7q in MDS patients without monosomy 7 or 7q deletion by conventional G-banding cytogenetics: does -7/7q- detection by FISH have prognostic value?

Chromosomal abnormalities are detected in 40-60% of patients with de novo myelodysplastic syndromes (MDS). This study used the FISH technique in 773 patients with de novo MDS without evidence of monosomy 7 (-7) or 7q deletion (7q-) by conventional G-banding cytogenetics (CC) to analyze their prognostic impact by FISH alone. FISH detected -7/7q- in 5.2% of patients. Presence of -7/7q- was associated with shorter overall survival than absence of such aberrations. Our results suggest that FISH 7q could be beneficial in patients with intermediate WHO morphologic risk stratification and no evidence of -7/7q- by CC.